In a system involving a body of liquid to which a treating agent is added, maintaining the proper feed level for the agent is essential for optimal performance. Improper feed rate of treating agent can lead to serious problems. For example, severe corrosion and/or deposit formation can rapidly occur on heat-exchange surfaces in cooling and boiler water systems when incorrect level of treating agent is used. One common method of estimating the concentration of a treating agent focuses on measuring the level of an active component in the treatment formulation (e.g. polymeric scale inhibitor, phosphate, or organophosphonate). That technique is often unsatisfactory due to one or more of the following problems:
background interferences from the system liquid or materials contained in the liquid; PA1 analytical methods use bulky and costly equipment; PA1 time-consuming, labor-intensive analyses are not compatible with continuous monitoring; PA1 inaccurate readings result from degradation or deposition of active component within the system.
An alternative method of determining treatment feed rates is to specifically add metal ions (e.g. Li.sup.+) to the formulation or system. That method helps circumvent the degradation/deposition and background interference problems. However, quantitation of low tracer levels commonly magnifies problems associated with expensive equipment and time-consuming test methods. Additional factors which must be considered are cost and environmental acceptability of the tracer. For example, radioactive tracers are detectable at very low levels, but are generally expensive and unacceptable due to environmental and health concerns.